In the computer industry, no sooner does one technology arrive than someone is already talking about its replacement. Take Itanium, Intel's first 64-bit processor, announced in late May. The chip is only now finding its way into the server and workstation markets, but Intel is already hyping McKinley, the Itanium successor due to arrive in systems during the first half of 2002.

Last week, at one of its regular Developer Forums, where software and hardware developers and other industry experts convene to learn about the latest Intel technologies, the company unveiled the inner workings of the McKinley architecture. Intel claims the chip may run certain software applications twice as fast as Itanium.

"McKinley is expected to perform one and a half to two times better than Itanium is currently performing," said Barbara Grimes, an Intel spokesperson. According to tests run by Intel, the new chip scored roughly 70 percent higher than Itanium under SPECint2000, a respected industry benchmark test that measures performance using integer-based--as opposed to floating-point--software. Kevin Krewell, a senior analyst with research firm MicroDesign Resources, confirms that McKinley will offer much better integer performance than its predecessor.

Intended for servers and workstations, McKinley uses essentially the same core architecture as Itanium, benefiting from the IA-64 instruction set codeveloped by Intel and Hewlett-Packard and from Itanium's new EPIC (Explicitly Parallel Instruction Computing) technology, a means of processing multiple instructions in parallel. To improve on Itanium, Intel has not only raised the core clock speed, but also installed a faster, wider front-side bus, revamped the caching subsystem, and made several other enhancements to the core logic.

Whereas the fastest Itanium chip has a core clock speed of 800 MHz, McKinley runs at 1 GHz. The most important improvement in the platform, however, is the new system bus. Itanium, when paired with Intel's 460GX chipset, uses a 266-MHz, 64-bit bus, providing 2.1 Gbps of bandwidth. When the chip was first being developed in the late 90s, 2.1 Gbps was a healthy amount of bandwidth, but by today's standards, it's subpar. McKinley uses a 400-MHz, 128-bit bus and offers 6.4 Gbps of bandwidth.

Intel has made similar improvements to McKinley's cache subsystem. The chip offers 32K of level 1 cache with a 1-clock latency, 256K of level 2 cache with a 5-clock latency, and 3MB of level 3 cache with a 12-clock latency. Itanium has the same amount of L1 cache and slightly more L3, but its cache latencies are much higher and its L3 cache, unlike McKinley's, sits on a cartridge outside the processor die. Consequently, McKinley has significantly more cache bandwidth. "Itanium has 11.7-Gbps bandwidth, and McKinley will offer 32-Gbps," says Grimes.

The new chip also offers additional integer units and issue ports, juggling more instructions at any given time. "With Itatium, you can do two loads or two stores per clock," continues Grimes. "On McKinley, you can do two loads and two stores."

All this is simply another way of saying that McKinley will outperform Itanium. The 70 percent improvement of McKinley over Itanium reported by Intel was not with a version of SPECint2000 compiled specifically for McKinley, but with one compiled for Itanium. Applications could achieve greater gains when recompiled for the new processor. "That's why we say the chip will be one and a half to two times faster," says Grimes. "Performance improvements depend on the application and how it's been recompiled."

Because the chip promises to be faster than Itanium and because it will reach the market in only a matter of months, many IT managers and other server buyers have been reluctant to purchase Itanium systems. "If McKinley was four years down the road, it would be a different story," says Steve Greenberg, a server market analyst with research firm ARS, "but as it stands, most people are waiting for McKinley to arrive before buying a 64-bit Intel processor."

Others are waiting because any bugs that show up in the Itanium platform should be ironed out before McKinley ships. "This is a brand new platform," says Greenberg. "IT managers don't want to buy until it's been on the market for a while and they see what kind of problems arise." It's the classic story. Why buy today's technology when tomorrow's will be better?

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